1. Field of the Invention
This invention relates to vehicle suspensions and, in particular, to a front suspension for coupling a steer axle assembly to a vehicle frame.
2. Discussion of Related Art
A conventional vehicle includes a vehicle frame having a pair of longitudinally extending frame rails that support the vehicle engine and body. The frame is supported on a plurality of ground-engaging wheels that are disposed at opposite ends of a plurality of axles. The vehicle may contain, for example, a steer axle on which the wheels are steerable by the vehicle operator and a drive axle whose wheels are driven by the vehicle engine. Each of the axles are coupled to the vehicle frame through a suspension that dampens movements transmitted between the wheels and the vehicle frame.
One conventional suspension includes leaf springs disposed on opposite sides of a vehicle with each leaf spring coupled to the vehicle frame at first and second ends and to an axle beam intermediate the first and second ends. This conventional suspension has several disadvantages. During braking, movement of the axle causes the leaf springs to wind up producing a caster change in the axle and a reduction in steering stability. This problem is expected to become greater as mandatory vehicle braking distances are reduced and, consequently, vehicle braking loads increased. Conventional vehicle suspensions must also account for lateral movement of an axle and offer a degree of lateral stability as well as roll stiffness to the vehicle. These objectives are sometimes achieved by using a track or stabilizer bar coupled between the frame and a component of the axle or suspension. These conventional suspensions, however, can interfere with vertical motion of the axle and create additional stress on some suspension components such as the above-mentioned leaf springs.
The inventors herein have recognized a need for a suspension for coupling a steer axle assembly to a vehicle frame that will minimize and/or eliminate one or more of the above-identified deficiencies.